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M. A. FRANKLIN, Administratrix. ELECTRIC CLOCK.

No. 550,959. l Patented Dec. 10,1895.

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ELECTRIC CLOCK.

Patented-DCC. l0, 1895.

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BENJAMIN FRANKLIN, OF CHICAGO, ILLINOIS, ASSIGNOR OF TIIREE-FOURTI'IS TO DAVID H. FLETCHER, GEORGE I-I. MERRIELL, AND CALVIN R, BEACH, OF SAME PLACE; MARY A. FRANKLIN ADMINISTRATRIX OF SAID BENJ A- MIN FRANKLIN, DECEASED.

ELECTRIC CLOCK.

SPECIFICATION forming part of Letters Patent No. 550,959, dated December 10, 1895.

'application led April l, 1893. Serial No. 46 8,748. (No model.)

To all whom it may concern:

Be it known that I, BENJAMIN FRANKLIN, of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Electric Clocks, of -which the following is a full, clear, and eX- act description, reference being had to the accompanying drawings, forming a part of this specification, in which corresponding' letters and numerals of reference in the different iigures indicate like parts.

The object of my invention is to so construct an electric pendulum clock that the train maybe actuated directly by the pendulum, the vibrations of which may be utilized for that purpose, while the electrical features and mechanical devices may be so arranged and combined with said pendulum as to enable an impulse to be imparted thereto whenever the arc of vibration of said pendulum is less than a given distance, all of which is hereinafter more particularly described and claimed.

In the drawings, Figure l represents a front view of the works of my improved clock. Fig. 2 is a like view, partly in section, showing the pendulum, a portion of which is removed in an opposite position from that shown in Fig. I. Fig. 3 is a like View showing the manner in which an impulse is imparted to the pendulum by the closing of an electric circuit to cause the return of said arm to its normal position; and Fig. 4 is a detail view in plan taken upon athe line 4, Fig. I.

Referring to the drawings, a represents the frame of my improved clock, from a stud in which is suspended in any well-known way a pendulum b, which is by preference arranged to straddle the hand and other arbors of the clock, substantiallyas shown, by using two rods attached to a cross-bar near the upper end of said pendulum instead of the single rod usually employed, although it is obvious that a single rod may be used by placing it so as not to interfere with the arbors. Mounted upon a suit-able arbor in the frame is an escapement or driving wheel c, a pinion upon the arbor of which serves to drive the usual train through which the hands are actuated. A gravity-pawl d is pivoted upon a suitable support, as shown, attached to one of the rods of the pendulum, said pawl being in engagement with the teeth of the wheel c, which it is intended to move the distance of one tooth with each vibration of Jghe pendu` lum. A gravity-arm cis pivoted to the frame at f and is also adapted to engage said teeth, being so adjusted that its end is free to drop behind each consecutive tooth as the escapement-wheel is advanced to its full limit by the pawl CZ. The object of said arm is not only to prevent a backward movement of the wheel c, but to aid in causing an impulse to be imparted to the pendulum when required, as hereinafter stated. A shoulder c is formed upon the under side of the arm e, slightly back of the end, to engage said teeth and pre'- vent backward movement of the wheel when the backward swing of the pendulum is not sufficient to permit the eXtreme end of said arm to drop behind a tooth.

Rigidly attached to the arm e or integral with the part to which it is attached is a secondary arm f, which is caused to vibrate up and down in unison with the arm e as the latter is lifted and permitted to fall by the movement of the teeth of the escapementwheel. Said arms thus joined form an elbowlever, the movement of which is indicated by the dotted lines shown in Fig. l. Pivoted at h upon a cross-bar g, which is rigidly secured to the pendulum-rods, is an arm e', loosely connected by means of a slender wire or cord j to the outer end of the arm f, as shown, so that as the latter rises and falls in the manner described the arm i is caused to rise and fall with it. The arm t' is bent at right angles at its outer end, as more clearly shown in Fig. 4, forming a hook 7c, which is adapted at the proper time, as hereinafter set forth, to engage with a stud m, arranged to project rearwardly from the lower end of the depending arm Z of an elbow-lever n, which is pivoted to the frame, as shown, and which I term the impulse-lever. The stud m is notched in its outer face, so as to insure its engagement with the part 7e at the proper time. The secondary arm o of said elbow-lever is extended horizontally, as shown. Parallel, or substantially so, with the arm o is an arm A79, which I denominate the impulse-arm, because of the manner in which it coaets with the impulse-lever. The impulse-arm is attached to the frame by means of an intervening spring q, which is so adjusted as to cause the end of the impulse-arm to press downwardly for the purpose of actuating the impulse-lever. A detent 9" is formed upon the end of saidimpulse-arm, which is adapted when the arm is raised to be engaged by means of a spring-catch s, that serves to hold the arm raised, as shown in Fig. l. A small elbow-shaped lever forming a latch 1f is pivotally mounted in a depending portion of the arm p, one arm of said latch being adapted to engage with the spring s, while the other lies in the path of movement of and is free to be engaged by the end of the arm 0 of the impulse-lever. The raising of said arm lifts the horizontal arm of the latch, which throws the vertical arm against the spring s, thereby releasing said spring from contact with the detent r and permitting the impulse-arm to be depressed against the arm o.

An electromagnet u is mounted upon the frame a, the armature c of which is attached to a lever zu, which is pivoted, as shown, to the frame, the other end of said lever being connected by means of a link ,fr to the impulse-arm p. Contact-pieces y ,5 are provided, the latter being a light spring, while the former of which is attached to an insulated metal stud secured to the frame, as shown, and in electrical contact with one terminal of the electromagnet,\vl1ile the other is attached to the impulse-arm p. T he source of electricity preferably consists of a battery l, one pole of which is connected with an insulated binding-post 2, connected in the usual way with the magnet u, while the other pole is connected with a binding-post 3 in direct contact with the metallic frame of the clock. The electric circuit is normally open; but when the contact-pieces y ,e are in contact, as shown in Fig. 3, the current is free to pass from the battery to the post 2, thence through the coil of the magnet, thence by an insulated wire to the contact-plate y, thence through contact-piece z, arm p, and frame to the post 3, and back to the battery.

The operation of my improved clock is as follows: The pendulum being set in motion, the pawl d is drawn back with the backward swing of said pendulum until it drops behind and engages a tooth in the wheel c. IV ith each forward movement of said wheel, consequent upon the like forward movement of said pendulum, the end of the arm e rides over the tooth with which it is thenengaged and drops behind it. As long as this complete movement of the arm c continues-that is to say, as long as the vibrations of the pendulum are of a sufficient length to permit the extreme end of said arm to descend to its full limit-the hook or part 71; upon the end of the arm t' is not permitted to engage the stud m upon the arm Z of the impulse-lever but with each forward movement of the pendulum the arm t' is lifted by the raising of the arm f consequent upon the passage of the arm e over a tooth of the wheel c. The normal movement of the arm i is clearly indicated in dotted lines in Fig. l. This causes the part 7c to pass alternately over and under the stud m in the path indicated by said dot-ted lines. As soon, however, as the swing of the pendulum is sufficiently shortened to cause the eXtreme end of the arm e to remain upon the point of a tooth when the pendulum has reached the extreme limit of its forward movement, as shown in Fig. 2, then upon the backward swing of the pendulum the part 75 is brought into engagement with the stud m, and the impulse-lever is in turn vibratcd with the pendulum, as indicated in dotted lines in said last-named figure. This movement causes the end of the arm o of the impulselever to be lifted into engagement with the latch t, thus forcing the spring-catch s out of engagement with the detent r and releasing the impulse-arm p, which, through the action of the spring q, depresses the arm o, and through the arms Z and t' imparts a sufficient impulse to the pendulum to cause it to swing to the full limit desired. Should it fail, however, to do so, the impulse will be automatically repeated until the full swing of the pendulum is attained, when the impulse-arm and lever are permitted to rest until their action is again required to restore the pendulum to its normal length of vibration. The depression of the impulse-arm causes the contactpieces y ,e to be brought together, thus closing the electric circuit, which, as stated, is normally open. The electromagnet being thus excited the armature c is attracted, which serves to aetuate the lever w and restore the impulse-arm to its normal position before the pendulum commences its backward swing.

In lieu of the spring q it is obvious that the impulse-arm may be weighted and its gravity alone employed to give impulse to the pendulum but I prefer to employ a spring, as it is not only lighter, but its tension may be readily adj usted in various well-known ways.

It will be observed that the only work imposed upon the battery is to lift the impulsearm to its normal position when displaced therefrom. As this requires but little power, and as the circuit is closed only at comparatively long intervals, the work upon the battery is reduced to a minimum. In an operative clock, from which the accompanying drawings, with the exception of slight changes, were made, the electric circuit is closed upon an average about once in three minutes, though it is obvious that this time would vary with the length of the pendulum and more or less with the varying amount of friction in the train, as well as from the varying conditions of the atmosphere. As the ICO IIO

impulse is given to the pendulum only when needed, it follows that said impulse is not regular, but only approximately so. This is an important advantage, in that it enables the pendulum to conform to the varying conditions of the atmosphere, which insures a more perfect measurement of time.

It will be observed that the primary driving power of the clock is purely mechanical, electricity being brought into action only for the purpose of storing power. As the train is driven by instead of being employed to drive the pendulum, the friction is scarcely appreciable, While the wheels may be made light, small, and may be few in number. The cost of making, therefore, as well as that of driving the clock is greatly reduced in comparison with that of those heretofore in use.

Having thus described my invention, I claiml. The combination in an electric clock., of a train, a driving-wheel therefor, a pendulum in operative connection with said drivingwheel, an impulse-lever, means for bringing the latter into connection with the pendulum when the arc of vibration thereof is shortened below a given limit, an impulse-arm for actuating said impulse-lever, means for holding said arm in a normal position, means, in operative connection with said impulse-lever for releasing the impulse-arm, a source of electricity, a normally open circuit, a circuitmaking and breaking device, and an electromagnet, the armature of which. is in operative connection with said impulse-arm, substantially as described.

f2. The combination with an electric clock in which the train is driven by the action of the pendulum, of the wheel c, in operative connection wi th said pendulum, elbow-lever having arms e and f', arm t' connected therewith, impulse-lever having arms Z 0, impulse-arm p, means for normally locking the latter under tension, a latch for releasing the same by the action of the impulse-lever, an electro-magnet having its armature connected with the impulse-arm, a source of electricity, contactpieces y 5, and suitable electrical connections, substantially as described.

3. In an electric clock,the combination with an impulse-producing mechanism arranged t0 e', an impulse-lever, and means for bringing` the arm fr into contact with said lever when the wheel c,is not moved sufficiently by the pendulum to permit the end of the arm e to fall behind a given tooth, substantially as described.

4L. The combination with a clock train, of a driving-Wheel, means for actuating the same step-by-step as the pendulum is vibrated, a pivoted lever adapted to ride over the teeth of said wheel, the fall of which is greater or less according as said wheel is moved to a given extent or falls short thereof, an arm connected to said lever and loosely attached to the clock pendulum, an impulse-lever in operative proximity to said arm, said arm being so adjusted as to engage said lever only when the driving-wheel falls short of its full normal movement, a spring-actuated impulsearm, means for holding the same in a normal position, means for releasing the same bythe action of the impulse-lever, an electro-inagnet having its armature in operative connection with said impulse-lever, a source of electricity, a normally open circuit, a circuitmaker and breaker, and means for closing the circuit when the impulse-arm is released, substantially as described.

5. The combination with a driving-wheel,of a pendulum in operative connection therewith, a pivoted elbow-lever adapted to ride over and be vibrated by the movement of the teeth of said pendulum, arm e', loosely connected with said elbow-lever, hook k, an impulse -lever having a stud m, an impulsearm in operative proximity thereto, electrical mechanism in operative connection therewith for lifting the same to a normal position immediately after its release, a spring-catch for holding the same, and means for releasing said catch by the action of the impulse-lever, substantially as specified.

In testimony whereof I have signed this specification, in the presence of two subscribing witnesses, this 28th day of March, 1893.

BENJAMIN FRANKLIN.

lVitnesses:

D. I-I. FLETCHER, A. L. FLETCHER. 

